1. Field of the Invention
The present invention relates to a drawing method for an electronic blackboard having a copy function for copying an image from a screen sheet onto recording paper, as well as a drawing function for drawing on the screen sheet an image read from an original document.
2. Description of the Relevant Art
Conventionally, there has been known an electronic blackboard which has a drawing function for drawing (printing) on a screen sheet an image read from an original document, in addition to a copy function for copying and printing on recording paper an image read from the screen sheet.
In such an electronic blackboard, since an endless screen sheet extends between and is wound around a pair of separated transport rollers (drive and follower rollers), during use, only the front half of the screen sheet appears as an available face, and the remaining portion is concealed within a cabinet as a stored face. Therefore, when the drawing function is used in a state in which an image remains unerased on the stored face concealed within the cabinet, an image read from the original document is written over the unerased image on the screen sheet.
An electronic blackboard which can prevent such overwriting is proposed in Japanese Patent Application Laid-Open (kokai) No. 8 (1996)-156491. In the electronic blackboard disclosed in the publication, write means is disposed inside the blackboard to be located close to the screen sheet; image erasing means is disposed in the vicinity of and on the upstream side of the write means with respect to the travel direction of the screen sheet; and written images are erased immediately before writing operation is performed by the write means, to thereby prevent overwriting.
However, the above-described conventional electronic blackboard has a serious drawback in that even in the case where an image remaining unerased on the stored face of the screen sheet must remain unerased, the unerased image is automatically erased if a person who is unaware of the situation uses the drawing function. In order to solve such a drawback, there may be provided means for detecting an image remaining unerased on the stored face of the screen sheet. However, in this case, an additional mechanism is required. Resulting in increased complexity and increased cost.